Project Summary/Abstract The overall goal of the proposed research program is to design and develop a noninvasive device for accurately measuring arterial compliance. Arterial compliance has been shown to be a strong indicator of many types of vascular disease, including cardiovascular disease, peripheral vascular occlusive disease, diabetes, renal failure, and aging. However, current imaging modalities and non-invasive methods of compliance measurement are limited by poor resolution, sensitivity and robustness. The proposed arterial elasticity imaging (AEI) device overcomes these limitations, producing real-time images of local arterial strain and near-real time elastic modulus results. High precision, direct measurements of vessel tissue motion using ultrasound tissue tracking will be combined with lumen pressure equalization. Using speckle tracking techniques, sub-micron precision measurements of tissue motion will be produced with fine, sub-millimeter, spatial resolution in a localized region, allowing direct intramural strain estimation of targeted vessels. In addition, external preloading will significantly improve sensitivity over measurements at physiological pressure conditions, by increasing the strain induced by the vessel pressure pulse. By combining pulse wave velocity (PWV) measurements using speckle tracking with intramural strain estimates, the vessel elastic modulus will be reconstructed with significantly reduced error from geometrical uncertainties and boundary conditions. Real-time display of tissue strain images and tracking metrics will provide "as needed" assessment and valuable feedback information to the user. This technology will fully characterize nonlinear elastic properties in a highly localized region, and provide vascular compliance assessment over a large strain dynamic range with very high precision. The main technical challenge facing device development is providing real-time tissue tracking, which is needed for intramural strain and PWV measurement. Cross correlation based speckle tracking methods require significant computational power, historically limiting them to off-line (i.e., not real-time) processing. Pixel Velocity Incorporated has developed algorithms and methods that combined with modern multi-processing computer hardware will provide computational power and flexibility needed for real-time arterial elasticity measurements in a portable ultrasound device.